This invention relates to flexible polyurethane foams. This invention further relates to a novel blowing catalyst composition for preparing flexible polyurethane foams.
It is known to employ both organic and inorganic tin compounds as the "gel" or polymerization catalyst for flexible polyurethane foams prepared by reacting a polyol with an isocyanate in the presence of a small amount of water. The water reacts with some of the isocyanate to form carbon dioxide, which becomes entrapped within the isocyanate-polyol reaction mixture and causes the resultant foam to rise. In order to prepare a useful foam that is substantially free of structural defects, it is usually necessary to employ a separate catalyst for the isocyanate-water reaction in order to balance the rates of this reaction and the isocyanate-polyol reaction. This catalyst is conventionally referred to as a "blowing" catalyst. A variety of compounds have been employed as blowing catalysts in combination with an inorganic tin compound such as stannous octoate as the gel catalyst. Conventional blowing catalysts include tertiary amines, and alkali metal salts of carboxylic acids. U.S. Pat. No. 3,620,985 teaches that the isocyanate-water reaction can be effectively catalyzed using combinations of certain antimony compounds with a base and a nitrogen-containing organic compound or the reaction product of said base with the nitrogen compound. Useful reaction products include sodium and potassium salts of amino acids, amidoximes and hydroxamic acids.
Surprisingly it has now been found that the reaction product of a base with a nitrogen compound specified in the aforementioned patent can be replaced by a potassium salt of a carboxylic acid containing from 2 to 20 carbon atoms. These compounds act synergistically with antimony (III) salts of carboxylic acids to yield unexpectedly short rise times when used in combination with a stannous salt as the gel catalyst for preparing flexible polyurethane foams.